Wombat Dyno

[DGardner]

Back home from my trip on my road bike to Nevada, California, Oregon, Idaho and back to Utah. I stopped at hodaka days for the first three days of rides and the wombat performed just great. The bike could use a bit more over rev but the torque was a blast on the trail's of the bad rock ride. Ed and some other people rode it and it was fun to see them come back in with big smiles.

[DGardner]

How will the piston last longer? The Yamaha piston? And how will the engine remove heat more efficiently?
Thanks, Dave

Dave...I think what Kel's is talking about is the two ring piston. Kel's and Tim both say that a two ring piston will work better for what I intend to use the bike for (long road rides). I guess from what I understand is a two ring piston will run cooler and transfer more heat to the cylinder.

[Modracer70]

Thanks, that makes sense, don't the new Hodaka pistons have 2 rings?
Dave

[DGardner]

The new model 97 I got was a single ring piston.

[DGardner]

Here is the dyno run we made today with the circle F pipe and the Boyesen duel reed and 03 manifold. It cost's $75 to make three pulls on the dyno and I had used all three so I never got a chance to put other reed's and a open manifold on to see what it would do. The second sheet is of a bone stock 72 wombat and the run I made today. The first one has today's in blue last years in red and Tim's pipe is in yellow.....that one is fun to ride.

[Bullfrog]

I hope the development project continues in the attempt to extend the power curve of the set-up which had major muscle at lower rpm's - that is wayeeeee more interesting than the "normal" (and very strong) power curve you have right now. (at least to me)
Ed

[DGardner]

We're working on the circle F pipe to lower the Max Torque RPM. One thing about the pipe Tim made that is interesting is there is a big difference between 10 and 11 foot pound of torque on the butt dyno.

[DGardner]

Like street outlaws........I did a test hit on the wombat today.

[viclioce]

Doug. I'm trying to understand a few things here. What rear tire size are you running on the 125? I'm assuming it's still an 18" wheel. So what's the diameter with the tire fully inflated? Also what sprockets are you currently running? You mentioned something about a 16/47 combo. Is that what you ran the dyno with on the bike? Curiosity has me asking for clarification. ; D Victor

[viclioce]

KELS. There isn't any need to get nasty. It seems to me that Greg was pointing out a reasonable approach. One usually does try to limit change to one item at a time to ensure you know what change is being caused by what implementation, if for no other reason than to be able to back out of the change if the effects are negative.

When I was having carb issues with my Wombat, lots of folks gave suggestions. One person even looked at the carb & sent it back to me. Greg chose to remedy the problem. He sent me a functional carb and then went on not only to repair the flaw in the old one but improved its function. I know he has been doing this kind of motor work for well over 30 years and is straight forward about problem solving. ; D Victor

[DGardner]

Victor.....Please don't call anyone out...there's been no problems on the forum for a couple weeks and we don't need one. On my 125 I'm running a 18" wheel with 3.50 rear tire with 16/47 sprockets. Thanks DG

[Bullfrog]

Vic,

The person who looked at your faulty carb found what was wrong, and offered to fix it -- but you gave direct instructions to send it back in its current state immediately so you could "pirate" parts out of it to use in another carb. That same person even included cash with the carb to pay for sending the carb back in order to do the repairs after the parts removal was completed. I have direct knowledge that the person wanted to make the carb reliable, serviceable and safe to use . . . but he never got the chance. He is still wondering why.
Ed

[rlkarren]

I’ve been thinking about this for awhile and have debated long and hard whether to write or not because I care not to perpetuate the flame war, but also feeling a sense of obligation to share my experiences with Doug’s Wombat 125cc. I can already hear the groans from bring this topic back to the top, but what I’ve ridden and experienced is prima facie evidence to me that something is right.

Yesterday, Doug and I went for a ride. No particular destination, just a ride. It was quite hot and I could tell the heat had an adverse affect on the performance of my bike. Along the way Doug suggested we switch bikes. I said SURE!! Since his always easily leaves me sucking his dust, (literally, in a hot day) and, I get a opportunity to get a well seasoned rider on mine to help me identify anything I could adjust.

Now I know some of you took a test ride at Hodaka Days this past June and were quite impressed.. But Doug has made a few adjustments since then. I’m not a very technical person and when people start talking about porting this or that, raising this port, lowering that port, I’m still quite fuzzy. What I do know is how it performs by “seat of the pants” experience.

This bike is a monster! A Hodaka bullet bike! For example, low end torque is amazing and it keeps pulling all the way through the throttle range. The power band hit at very low rpm’s, (seems like it was about 3800 - 4000 rpms, and hit like a NOS boost. I’ve ridden some well built Super Combats and even a 98 Super Rat to have something to compare it to, but when the power band hit on Doug’s Bike, hang on! Holy Shnikies!

I hit 55mph in 4th gear, before needing to shift into 5th. Shifting into 5th gear launched me up to 67 mph and about 6800 rpm's before I backed off. And even then I was only between 1/2 - 3/4 throttle. Cruising speed! Ya know, that happy spot where the bike seems to like to cruise. Another thing I notice is that it just doesn’t bog down… No matter which gear I’m in, if I need to “punch it”, it punches and goes! Up hill with a head wind didn’t seem to conquer this monster either! Sure, there was a little bit of slowdown, but I’m still climbing at a comfortable speed WITH traffic at 55 - 60 mph with lots more room to accelerate still!

What I keep in mind is that performance like this is gained using 16/47 sprockets with stock aluminum wheel sizes. Very tall gears. In my mind, this equates to incredible torque. I kid you not, if you ever thought what a Hodaka bullet bike would look like, this is probably it. I think Doug has very likely built this engine to it’s fullest potential and not meaning or even trying to fan the flame, but I’m convinced Kelsey and Tim know what they’re doing. If they can get me even half the performance of Doug’s bike in mine, I’m all over it!

You can remain skeptical all you want, and that's fine, but I'm fairly confident that Doug would be more than happy to invite you to take a ride and then I'm also confident you'll be on board also after you're able to wipe the perma-grin off your face.

$0.02

Roger

[Dale]

Good stuff Roger. I appreciate your post and also appreciate Doug keeping us updated on his quest. There is no need for anything but admiration for people that spend their time and money in an effort to develop a special bike such as this.

Having two Wombats myself, I know that they are less than impressive when bone stock. I am working with a friend to improve my carburetor with vanes and a UFO in hopes of making it a better rider. Initial results are very promising. I will just be happy to have a stock Wombat that runs smoothly throughout the throttle range. Kudos to Doug and his team taking a Wombat to a whole new level.

My 2 cents!
Dale

[Kels]

Doug... I think we need to get it back on the dyno with the new KTM piston

[Modracer70]

Doug, what oil do you use and mix ratio, what octane gas?
Thanks, Dave

[DGardner]

Dave

I use premium pump gas with 20:1 oil mix. The oil I use is power mist....Hi Rev....I'm on my 3rd gallon for the year with no problems. I have looked in the motor a couple times, there is very little carbon with very good oil on all the parts. DG

[thirdstone]

The Blue lines look like more fun to me

[thirdstone]

Like street outlaws........I did a test hit on the wombat today.

Ed this is interesting. I have pluged this in to the spreadsheet we did a while ago and we are in the ballpark. DG what was the RPM at this speed and we would also like to know the radius of the tyre ,ie the distance from the center of the axle to the ground.
16/47 at 7000rpm with radius of 36cm gives 71.54mph

[thirdstone]

The piston we used was for a 1978 - 1981 DT125.....Oh and the hodaka cylinder started out as a model 03 aluminum cylinder.

Good to hear that you found an alternate piston setup, although with the excelant Wiseco pistons that SH had made up it`s no longer that urgent.
I thought that the yam piston was /is a 16mm pin and the Hodaka rod is made for a 14mm pin. How did you adapt the piston ? I tried to solve this a few years ago but couldn`t get it done with out changing the rod. That was too big a deal at the time. From memory the pin to crown distance was within 1 mm so that could be delt with.

Thanks

Kev

[DGardner]

Like street outlaws........I did a test hit on the wombat today.

Ed this is interesting. I have pluged this in to the spreadsheet we did a while ago and we are in the ballpark. DG what was the RPM at this speed and we would also like to know the radius of the tyre ,ie the distance from the center of the axle to the ground.
16/47 at 7000rpm with radius of 36cm gives 71.54mph

Kevin
The Highest RPM was around 8500 RPM. I will get the rear tire size and post later. DG

[thirdstone]

The spreadsheet at 8500rpm MAKES 77.21mph at 16 47 gearing and wheel radius of 32cm

[Kels]

So, I am curious here... What exactly are you (thirdstone) trying to decide??

It APPEARS that you are trying to decide if Doug is lying about his speed achieved?

So I, politely ask.. What are you trying to determine?

[DGardner]

The spreadsheet at 8500rpm MAKES 77.21mph at 16 47 gearing and wheel radius of 32cm

I checked and I came up with 33cm from center of axle. I set the bike on a stand then used a level to get the top of the tire to the center of the axle. DG

[DGardner]

The Blue lines look like more fun to me

The pipe that we used for the blue line dyno run was a fun one to ride. We have changed some stuff from the last dyno run and it is running better now with than ever. My friend (Tim) that made the pipe and did the dyno run's is having some health problems....so all dyno and pipe making is on hold till we can get him feeling better. DG